Rheostat.



Patented use. 2, |902.I F. MAcKmrosH.

BH EOSTAT.

[Application Mod Kay 81, 190i.)

(No Model.)

Fig. 2.

InVen-Tor:

Wckmth UNITI-3D STATES PATENT OFFICE.

FREDERICK MAVKINTOSII, ()l` Stllliflt'VAIlY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION F NIHV YORK.

RH EOSTAT.

SPECIFICATION forming part of Letters Pat/ent No. 714,927, dated December 2, 1902.

Applicltlon Bled Kay 31,1901.

To (1N 'r11-ont if muy concern.:

lle it known that I, 'Fitnnmucii MACHIN- TOSII, a citizen of theUnited States, residing,y atScheneetady, county of Schenecmdy, State ot' New York, have invented certain new and useful Improvements in Rhcostats, of which the following is a specification.

This invention relates` to electric rhcostats, tho object being.v to provide an instrument of this character ot very compact construction and cheap to manufacture and low heating. In carrying ont the invention I form the resistance units of the rheostat ot punchednietal grids, which are coated with insulationY heat-refractory enamel, except-at the ends, where thc connections arcA made` and I clamp a plurality of these grids together with intervening.: metal radialing-plates. 4 The grids-*are lnounted on rods secured in a support ing:- trame, and the radiating-plates are kept iu place by interlocking,Y projections between the grids and the plates. Taps are taken from the ends ot certain grids and led to contactstuds mounted on a switch-plate, hy which' the amount of the resistance is `.'aried.

-Tho invention involves various features of novelty` which will bc hereinafter pointed ont in the claims.

Inthe accompanying:drawings, which illustrate the invention, Figure 1 is a side elevation, partly in section, of a rheostat embodying my improvements. Fig. L is a bottom plan View, partly in section; and Fig. 3 is a sectional detail showing,r the plan of interlocking the grids and radiating-plates.

1 1 1" lc represent the feet at a support-- ing-frame, upon which the gzlds of the-rheostat are mounted. This is connected to a slate or marbletop plate 2, in which are mounted contact-studs, as indicated in l-ig 1, from which lead conductors 3 3, the., to different scctionsof the .f toupcf grids. Overthe contacts sweeps a brush 4, as usual, to vary the amount o f resistance in the circuit. 'lho resistance-wills are formed of pnnchings, as 5, from sheet metal, provided with supporting-V arms 5 5l, adapted to be slid over a bar or rod G,covcred with insulating material. The` Serial No. 52.634. (No model.)

grids are enameled, except at the ends. 5 5b, which latter are not coated. After boing punched or duringY lhe punching operation longitudinal ribs are strut-k up at encor more points in the grids, as indicated at 7 7, adapt ed to aline with correspondan depressions in lmetal radiating-platen K, which are placed bet wecn the several grids. The desired tiltinher of the grids and plates are assembled, as indicated iu Fig. :2, and clamped together by hars Si 9, which are also mounted on the support i lig-rods G G". The several grids are alternately connected at the ends, so as to forni an uninterrupted circuit from end to end of the grids, insulated washers 1011 heini: in-

serted between alternate pairs of grids at the two ends. Connector-clips l2 aro secured to the grids at iutcrvalsatone end, to which may lie connected the leads Ii 3, connecting with the several contactstuds. The alternate joints-` at. one side of the group of grids may he electrically connected by the connectors 12, and at the other end metalwashers 13 may be used. The other joints are insulated by mica washers 11. The grids and intervening; washers are assembled on insulatingbushings, as 14, around the rods ti G, the clamp-bars 9 and tl putin place, and the radiating-plates inserted, so as t-o bring the' projections in alineinent. The clamp-nuts 15 15 are then tightened, thus binding the several grids into close engagement with the radiating-plates and holding all parts solidly together. The rods may then he locked in place on the supporting-legs of the rheostats hy clamp-nuts, as indicated in Fig. 2. Circuit eonneetions with the terminals may be made, as usual. When tho switch 4 is moved over the contact-studs, a greater or smaller number ofthe grids is cut into circuit.

'lhe enamel on the grids prevents shortcireniting,a11d yet promotes good 4heat-dissipatiu.,r contact, with the intervening metal plates, while thc contact-faces ol' alternato gridson the snpportiiux-rods are held in close` engagement hy tho nuts 15 15, thereby in surim,r good contact. The heat-radiating plates are prevented from falling out by the interlocking devices described and are held in L'ood heat-comlnctive relation to the grids without interfering with the insulation.

What l claim as new, and desire to secure by Letters Patent of the United States, is-

l. A rheoslatcolnposcd of n plurality of resistance-grids, each coated with a thin adherent. layerof insulating-enamel assembled and clamped together with intervening heat-radiating plates.

2. A rheostat comprising a plurality of resistancegrids enameled with a refractory material except at the ends and held in contact with heat-radiating plates, and means for damping the several grids together at the ends to connect them in series.

3. A rheostntcomprisingapluralityofgrids covered with a thin insulating-enamel and held. in contact with intervening heat-radiating plates, interlocking projections heilig provided on the gridsand plates, to prevent relative movement.

4. A rheostat comprising a plnralityof resistance-grids formed of sheet-metal stampings each covered with n thin adherentinsulating-euamel and connected in series, heatradiating plates between the several pairs of grids insulated therefrom, and interlocking connections for preventing relative displace; ment..

5. A rheostat comprising a plurality of resistance-grids connected in series, each covered with a thin adherent insulating-enamel, heatradiating plates between the several pairs of grids insulated therefrom, and interlocking tonguo-nnd-groo\'e connections for preventing relative displacement.

6. A rheostat comprising a plurality ot resistance-grids each covered with a thin adherent insnlating-enamel connected in series relation, intervening heat-radiating plates interlocking with the grids, nud means for clamping them in firm engagement.

7. A grid for an electric rheostat having hare contact-faces at. its ends, and a coating of enamel on the body of the grid to serve as an insulat.ing-spacer.

8. A rhcostat provided with a plurality of resistance-grids each coated with a thin adhei-ent insulating-enamel mounted on supports at their ends and insulated therefrom, insulat-ing-wasllers between the several pairs of grids, insulated heatradiating plates between the several grids held in close contact therewith, and means for clamping the several parts in firm engagement.

9. A rheostat comprising a plurality ot ,ennmcled resistance-grids, insulated support.I ing-rods therefor, said grids being connected in series relation, metal platos between the grids mechanically interlocked therewith, clamping devices for holding the grids and plates under pressure, and connections with contact-studs from different parts of the grid series.

10. A rheostnt comprising a plurality of resistance-grids, insulated heat-radiating plates mechanically interlocking -therewith, supporting-rods threading perforations in the ends of the grids, and clamping devices for holding the parts in firm engagement.

In witness whereof I have hereunto set my hand this 27th day of May, 1901.

FREDERICK MACKINTOSH.

Witnesses:

BENJAMIN B. IIULL, FRED Russ. 

